The present invention, in some embodiments thereof, relates to polypeptides, polynucleotides encoding same, transgenic plants expressing same and methods of producing and using same, and, more particularly, but not exclusively, to methods of increasing plant yield, oil yield, seed yield, biomass, growth rate, vigor, oil content, abiotic stress tolerance and/or nitrogen use efficiency.
Abiotic stress conditions such as salinity, drought, flood, suboptimal temperature and toxic chemical pollution, cause substantial damage to agricultural plants. Most plants have evolved strategies to protect themselves against these conditions. However, if the severity and duration of the stress conditions are too great, the effects on plant development, growth and yield of most crop plants are profound. Furthermore, most of the crop plants are highly susceptible to abiotic stress (ABS) and thus necessitate optimal growth conditions for commercial crop yields. Continuous exposure to stress causes major alterations in the plant metabolism which ultimately leads to cell death and consequently yield losses.
The global shortage of water supply is one of the most severe agricultural problems affecting plant growth and crop yield and efforts are made to mitigate the harmful effects of desertificFation and salinization of the world's arable land. Thus, Agbiotech companies attempt to create new crop varieties which are tolerant to different abiotic stresses focusing mainly in developing new varieties that can tolerate water shortage for longer periods.
Suboptimal nutrient (macro and micro nutrient) affect plant growth and development through the whole plant life cycle. One of the essential macronutrients for the plant is Nitrogen. Nitrogen is responsible for biosynthesis of amino acids and nucleic acids, prosthetic groups, plant hormones, plant chemical defenses, and the like. Nitrogen is often the rate-limiting element in plant growth and all field crops have a fundamental dependence on inorganic nitrogenous fertilizer. Since fertilizer is rapidly depleted from most soil types, it must be supplied to growing crops two or three times during the growing season. Additional important macronutrients are Phosphorous (P) and Potassium (K), which have a direct correlation to yield and general plant tolerance.
Vegetable or seed oils are the major source of energy and nutrition in human and animal diet. They are also used for the production of industrial products, such as paints, inks and lubricants. In addition, plant oils represent renewable sources of long-chain hydrocarbons which can be used as fuel. Since the currently used fossil fuels are finite resources and are gradually being depleted, fast growing biomass crops may be used as alternative fuels or for energy feedstocks and may reduce the dependence on fossil energy supplies. However, the major bottleneck for increasing consumption of plant oils as bio-fuel is the oil price, which is still higher than fossil fuel [Hypertext Transfer Protocol://World Wide Web (dot) eia (dot) doe (dot) gov/oiaf/analysispaper/biodiesel/; Hypertext Transfer Protocol://World Wide Web (dot) njbiz (dot)com/weekly article.asp?aID=19755147 (dot) 6122555 (dot) 957931 (dot) 7393254 (dot) 4337383 (dot) 561&aID2=73678]. In addition, the production rate of plant oil is limited by the availability of agricultural land and water. Thus, increasing plant oil yields from the same growing area can effectively overcome the shortage in production space and can decrease vegetable oil prices at the same time.
Studies aiming at increasing plant oil yields focus on the identification of genes involved in oil metabolism as well as in genes capable of increasing plant and seed yields in transgenic plants.
Genes known to be involved in increasing plant oil yields include those participating in fatty acid synthesis or sequestering such as desaturase [e.g., DELTA6, DELTA12 or acyl-ACP (Ssi2; Arabidopsis Information Resource (TAIR; Hypertext Transfer Protocol://World Wide Web (dot) arabidopsis (dot) org/), TAIR No. AT2G43710)], OleosinA (TAIR No. AT3G01570) or FAD3 (TAIR No. AT2G29980), and various transcription factors and activators such as Lec1 [TAIR No. AT1G21970, Lotan et al. 1998. Cell. 26;93(7):1195-205], Lec2 [TAIR No. AT1G28300, Santos Mendoza et al. 2005, FEBS Lett. 579(20:4666-70], Fus3 (TAIR No. AT3G26790), ABI3 [TAIR No. AT3G24650, Lara et al. 2003. J Biol Chem. 278(23): 21003-11] and Wri1 [TAIR No. AT3G54320, Cernac and Benning, 2004. Plant J. 40(4): 575-85].
Zabrouskov V., et al., 2002 (Physiol Plant. 116:172-185) describe an increase in the total lipid fraction by upregulation of endoplasmic reticulum (FAD3) and plastidal (FAD7) fatty acid desaturases in potato.
Wang H W et al., 2007 (Plant J. 52:716-29. Epub Sep. 18, 2007) describe an increase in the content of total fatty acids and lipids in plant seeds by over-expressing the GmDof4 and GmDof11 transcription factors.
Vigeolas H, et al. [Plant Biotechnol J. 2007, 5(3):431-41] and U.S. Pat. Appl. No. 20060168684 discloses an increase in seed oil content in oil-seed rape (Brassica napus L.) by over-expression of a yeast glycerol-3-phosphate dehydrogenase under the control of a seed-specific promoter.
Katavic V, et al., 2000 (Biochem Soc Trans. 28:935-7) describe the use of the Arabidopsis FAE1 and yeast SLC1-1 genes for improvements in erucic acid and oil content in rapeseed.
U.S. Pat. Appl. No. 20080076179 discloses an isolated moss nucleic acid encoding a lipid metabolism protein (LMP) and transgenic plants expressing same with increased lipid levels.
U.S. Pat. Appl. No. 20060206961 discloses a method of increasing oil content in plants (e.g., in plant seeds), by expressing in the plant the Ypr140w polypeptide.
U.S. Pat. Appl. No. 20060174373 discloses a method of increasing oil content in plants by expressing a nucleic acid encoding a triacylglycerols (TAG) synthesis enhancing protein (TEP) in the plant.
U.S. Pat. Appl. Nos. 20070169219, 20070006345, 20070006346 and 20060195943, disclose transgenic plants with improved nitrogen use efficiency which can be used for the conversion into fuel or chemical feedstocks.
WO2004/104162 teaches polynucleotide sequences and methods of utilizing same for increasing the tolerance of a plant to abiotic stresses and/or increasing the biomass of a plant.
WO2007/020638 teaches polynucleotide sequences and methods of utilizing same for increasing the tolerance of a plant to abiotic stresses and/or increasing the biomass, vigor and/or yield of a plant.
WO2008/122890 teaches polynucleotide sequences and methods of utilizing same for increasing oil content, growth rate, biomass, yield and/or vigor of a plant.